This invention relates to an ink-jet recording apparatus having an ink-jet recording head capable of jetting ink from nozzles to form dots on a recording medium according to printing data. In particular, this invention is related to an ink-jet apparatus which can recover nozzles"" ability to jet ink by discharging ink with no relation to a printing operation from the nozzles.
As shown in FIG. 15, a general ink-jet recording head has: a plurality of nozzles 40 (although only one nozzle is shown in FIG. 15) and a plurality of pressure chambers 41 communicating with the nozzles 40 respectively. A piezoelectric vibrating member 42 is mounted on an outside surface of each elastic wall which partly defines each of the pressure chambers 41. The piezoelectric member 42 expands or contracts depending on a printing signal. Thus, a pressure in each of the pressure chambers 41 is changed to jet ink 44 from the pressure chamber 41 through the nozzle 40 as an inkdrop 45.
In recent apparatuses for printing color images, plural color types of ink may be used as the ink 44, which may include yellow ink, magenta ink, cyan ink as well as black ink. The nozzles 40 are arranged for each of the color inks.
In the above recording head, the ink 44 in the nozzles 40 may dry up to clog the nozzles 40 therewith while the recording head remains stopped after a printing operation. Then, the nozzles are sealed by a capping unit except while the recording head is in the printing operation. However, solvent of the ink 44 in the nozzles 40 may gradually evaporate to increase a viscosity of the ink 44 if the nozzles are sealed for a long time. In the case, it may be difficult to start a printing operation immediately. In addition, there may be some troubles, for example that quality of printed images may deteriorate.
During the printing operation, the nozzles 40 frequently jetting inkdrops 45 are scarcely clogged with the ink 44 because new ink 44 is supplied thereinto in succession. However, even during the printing operation, the nozzles 40 rarely jetting inkdrops 45, for example the nozzles arranged at an upper end portion or a lower end portion, are liable to be clogged with the ink 44 because the ink 44 in such nozzles 40 is liable to dry to increase the viscosity thereof.
To solve the above problems, a xe2x80x9cflushing operationxe2x80x9d or a xe2x80x9ccleaning operationxe2x80x9d is carried out by forcibly discharging the clogging ink 44 from the nozzles 40 in no relation to the printing operation, to recover the ability of the nozzles 45 to jet inkdrops. The above flushing or cleaning operation may be carried out when power supply starts to be given to the recording apparatus or when a first printing signal is inputted to the recording apparatus, as a preparatory step before the printing operation.
In the flushing operation, a driving signal in no relation to the printing data is supplied to the piezoelectric vibrating members 42 to jet the clogging ink 44 having a relatively increased viscosity from the nozzles 40. The cleaning operation is carried out when the ability of the nozzles to jet inkdrops is not sufficiently recovered by the flushing operation. In the cleaning operation, a suction pump applies a negative pressure to the nozzles 40 to forcibly suck the clogging ink 44 having a relatively increased viscosity from the nozzles 40.
The degree of the increasing viscosity of the ink 44 in the nozzles 40, i.e., the degree to which the nozzles 40 are clogged becomes worse depending on the length of the capping time for which the recording head remains sealed by the capping unit or the length of the total printing time until the recording head is sealed by the capping unit.
Therefore, as shown in FIG. 16, whether the flushing operation or the cleaning operation should be carried out is determined by the combination of the capping time and the total printing time. The flushing operation is carried out when the capping time or the total printing time is relatively short (see a flushing area in FIG. 16). The cleaning operation is carried out when the capping time or the total printing time is relatively long (see a cleaning area in FIG. 16).
As described above, the apparatuses for printing color images use the plural color types of ink including the black ink, the yellow ink, the cyan ink, the magenta ink or the like. The plural color types of ink have different evaporating rates of the solvent thereof. Thus, the respective degrees of the increasing viscosity of the respective types of ink are different even when the capping time and the total printing time are the same. That is, the nozzles may have a different ability to jet ink respectively, even when the nozzles are used in the same condition.
In addition, in the case of the above conventional apparatus, there is a uniform boundary condition for the cleaning operation or the flushing operation. Thus, the cleaning operation may be carried out for the nozzles jetting ink having a relatively low rate of increasing viscosity, even when the ability of the nozzles to jet ink can be recovered by the flushing operation. This may waste ink.
To the contrary, the rate of increasing viscosity of the ink may be too high to recover the ability of the nozzles to jet ink by the flushing operation. In the case, as shown in FIG. 17, a meniscus of the ink in the flushing operation may become unstable and dented deeply and obliquely to take an air bubble in the nozzle 40.
In addition, the nozzles are used for printing with different frequencies respectively. For example, in the apparatus for printing color images which uses the plural types of ink including the black ink, the yellow ink, the cyan ink, the magenta ink or the like, the nozzles for the respective color ink are used with different frequencies respectively. When a nozzle is used with a low frequency, i.e., when inkdrops are jetted from a nozzle at a low frequency, the ink in the nozzle is liable to dry and the viscosity of the ink is liable to increase. Thus, the degrees of the increasing viscosity of ink are different depending on the frequencies of using the nozzles even when the printing time is the same. That is, the nozzles may have a different ability to jet ink respectively, even when the printing time is the same. In the case of the above apparatus, the uniform condition for the cleaning operation or the flushing operation is defined in no relation to the frequencies of using the nozzles. Thus, the cleaning operation may be carried out for the nozzles whose ability to jet ink can be sufficiently recovered by the flushing operation. This may waste ink.
To the contrary, the rate of increasing viscosity of the ink jetted from the nozzles used with only a low frequency may be too high to recover the ability of the nozzles to jet ink by the flushing operation. In the case, as shown in FIG. 17, a meniscus of the ink in the flushing operation may become unstable and dented deeply and obliquely to take an air bubble in the nozzle 40.
On the other hand, the volume of the ink removed in the cleaning operation is larger than that in the flushing operation because the ink is forcibly sucked by the suction pump in the cleaning operation. Thus, it is preferable that the flushing area is as large as possible. That is, it is preferable that the flushing operation is carried out for the conditions of as highly an increasing viscosity as possible of the ink to recover the ability of the nozzles to jet ink. This can reduce the volume of the ink removed to solve the clogging and increase the volume of the ink saved to use for the printing operation. This can also reduce the volume of the wasted ink.
Of course, regarding the cleaning operation, it is also requested that conditions for the cleaning operation be set to reduce the wasted ink.
The object of this invention is to solve the above problems, that is, to provide an ink-jet recording apparatus that can carry out an efficient flushing operation or an efficient cleaning operation by changing the conditions for the flushing operation or the cleaning operation depending on the nozzles, for example depending on the nozzles for the respective types of the ink.
In order to achieve the object, an ink-jet recording apparatus includes: a recording head having a plurality of nozzles, the nozzles being classified into at least two classes, and a driver for causing ink to be discharged from the nozzles to carry out a recovery operation. A setting unit is provided for setting up volumes of ink which should be discharged from the nozzles in such a manner that a volume of ink which should be discharged from a nozzle of one class is set up separately from a volume of ink which should be discharged from a nozzle of another class, and a recovering operation controller is provided for causing the driver to carry out the recovery operation of the nozzles so that volumes of ink actually discharged from the nozzles are respectively coincident with the volumes of ink set up by the setting unit.
For example, the driver causes ink to be jetted from the nozzles to carry out a flushing operation as the recovery operation, and the setting unit sets up volumes of ink which should be jetted from the nozzles during the flushing operation in such a manner that a volume of ink which should be jetted from a nozzle belonging to one class is set up separately from a volume of ink which should be jetted from a nozzle belonging to another class. The recovering operation controller is a flushing operation controller which causes the driver to carry out the flushing operation of the nozzles so that volumes of ink actually jetted from the nozzles are respectively coincident with the volumes of ink set up by the setting unit.
Alternatively, the driver sucks ink from the nozzles to carry out a cleaning operation as the recovery operation, and the setting unit sets up volumes of ink which should be sucked from the nozzles during the cleaning operation in such a manner that a volume of ink which should be sucked from a nozzle belonging to One class is set up separately from a volume of ink which should be sucked from a nozzle belonging to another class. The recovering operation controller is a cleaning operation controller which causes the driver to carry out the cleaning operation of the nozzles so that volumes of ink actually sucked from the nozzles during the cleaning operation are respectively coincident with the volumes of ink set up by the setting unit.
The class may consist of a plurality of nozzles from which ink having a rate of increasing viscosity is jetted, or a plurality of nozzles classified on the basis of another feature, or only one nozzle.
The setting unit may set up the volumes of ink which should be jetted from the nozzles in the flushing operation in such a manner that a volume of ink which should be jetted from a nozzle belonging to a chosen class and which has a relatively greater rate of increasing viscosity is larger than a volume of ink which should be jetted from a nozzle belonging to another chosen class and which has a relatively smaller rate of increasing viscosity. In the case, when the ink has a relatively greater viscosity, a large volume of the ink can be jetted from the nozzle in the flushing operation to recover the ability of the nozzle to jet ink. Therefore, there is no problem caused by the difference in the rates of increasing viscosity depending on the types of ink and so on. On the other hand, when the ink has a relatively smaller viscosity, a relatively small volume of the ink can be jetted from the nozzle in the flushing operation to recover the ability of the nozzle to jet ink. Therefore, the volume of the waste ink can be restrained even when there is a difference in the rates of increasing viscosity depending on the types of ink and so on. The flushing operation can also make the starting of the printing operation stable. In addition, the flushing operation can prevent an air bubble from being formed in the nozzle from which the ink having a relatively greater viscosity can be jetted.
As described above, the flushing area, which represents conditions capable of recovering the ability of nozzles to jet ink by only the flushing operation, becomes larger than the conventional one by introducing the efficient flushing operation for the nozzles for the respective types of the ink respectively. Therefore, the volume of the waste ink necessary to recover the ability of the nozzle to jet ink can be reduced, and the volume of ink capable of being used for the printing operation can be increased. The total volume of the waste ink can also be reduced.
The flushing operation controller may control the number of inkdrops jetted by the driver. In the case, the numbers of times the ink is jetted in the flushing operation are predetermined for the respective types of the ink respectively. Such a flushing operation can be controlled very simply and easily.
In addition, the ink-jet recording apparatus may include a capping unit capable of sealing the nozzles of the recording head, and a capping time measuring unit for measuring a capping time for which the nozzles of the head are sealed by the capping unit. In the case, the setting unit may set up the volumes of ink which should be jetted from the nozzles in the flushing operation in such a manner that the volumes of ink are larger according to the capping time. That is, the degrees of the viscosity of the ink in the nozzles are judged by the capping time. This flushing operation can be easily controlled to recover the ability of the nozzles to jet ink very efficiently.
The ink-jet recording apparatus may also include a capping unit capable of sealing the nozzles of the recording head, and a printing time measuring unit for measuring a printing time for which the nozzles of the head are away from the capping unit to carry out a printing operation until the nozzles are moved back to and sealed by the capping unit. In the case, the setting unit may set up the volumes of ink which should be jetted from the nozzles in the flushing operation in such a manner that the volumes of ink are larger according to the printing time. That is, the degrees of the viscosity of the ink in the nozzles are judged by the printing time. This flushing operation can be easily controlled to recover the ability of the nozzles to jet ink very efficiently.
When the capping time or the printing time is compared with a plurality of predetermined times, the volumes of ink which should be jetted can be set stepwise to further reduce the wasted ink. The plurality of predetermined times can be different for the respective types of the ink.
The volumes of ink which should be jetted stepping up when the capping time is longer than a predetermined time may be larger for the nozzles jetting ink that has a greater rate of increasing viscosity. Similarly, the volumes of ink which should be jetted stepping up when the printing time is longer than a predetermined time may be larger for the nozzles jetting ink that have a greater rate of increasing viscosity. In these cases, the ability of the nozzles to jet ink can be recovered more surely by jetting the larger volumes of the ink when the ink has a greater viscosity because of the greater rate of increasing viscosity, the long capping time and/or the long printing time.
The ink-jet recording apparatus may include a jetting, number counting unit for counting respective numbers of times the ink has been jetted (i.e., the number of inkdrops jetted) from the nozzles belonging to the respective classes during a printing operation. In the case, the setting unit may set up the volumes of ink which should be jetted from the nozzles during the flushing operation according to the numbers of inkdrops counted by the jetting number counting unit.
In the case, when the ink has a relatively greater viscosity, a large volume of the ink can be jetted from the nozzle in the flushing operation to recover the ability of the nozzle to jet ink. Therefore, there is no problem caused by the difference in the rates of increasing viscosity depending on the frequencies with which, the nozzles are used. On the other hand, when the ink has a relatively small viscosity, a small volume of the ink can be jetted from the nozzle in the flushing operation to recover the ability of the nozzle to jet ink. Therefore, the volume of the waste ink can be restrained even when there is a difference in the rates of increasing viscosity depending on the frequencies with which the nozzles are used. This flushing operation can also make the printing operation stable. In addition, this flushing operation can prevent an air bubble from being formed in the nozzle from which the ink having a relatively greater viscosity can be jetted.
The setting unit may have: a coefficient determining part for determining coefficients according to the numbers of inkdrops counted by the jetting number counting unit, a provisional volume storage unit for storing a predetermined and provisional volume of ink for the flushing operation, and a calculating body for calculating the volumes of ink which should be jetted from the nozzles. In the case, the appropriate conditions for the flushing operation can be easily obtained. The flushing operation is easily controlled, too.
The ink-jet recording apparatus may include a storage unit capable of storing data whether the power supply is given or not. The storage unit can store the numbers of inkdrops (the jetting numbers) counted by the jetting number counting unit at the end of the printing operation. At the next starting of the printing operation, the setting unit can set up the volumes of ink which should be jetted from the nozzles during the flushing operation according to the numbers of inkdrops stored by the storage unit. In the case, the number of times the ink has been jetted in the previous printing operation can be taken into consideration for the flushing operation at the starting of the following printing operation. This flushing operation can recover the ability of the nozzles to jet ink very efficiently to make the starting of the printing operation stable.
The ink-jet recording apparatus may also include the capping unit capable of sealing the nozzles of the recording head, the capping time measuring unit for measuring the capping time for which the nozzles of the head are sealed by the capping unit, and the printing time measuring unit for measuring the printing time for which the nozzles of the head are away from the capping unit to carry out a printing operation until the nozzles are moved back to and sealed by the capping unit, as well as the jetting number counting unit. In the case, the setting unit may set up the volumes of ink which should be jetted from the nozzles in the flushing operation in such a manner that the volumes of ink are larger when either the capping time or the printing time is longer. That is, the degrees of the viscosity of the ink in the nozzles are judged by the capping time and/or the printing time, because the longer the capping time or the printing time is, the more the viscosity of the ink increases and the worse the ability of the nozzle to jet ink deteriorates. The setting unit may also set up the volumes of ink which should be jetted from the nozzles in the flushing operation according to the number of times the ink has been jetted. This flushing operation can recover the ability of the nozzles to jet ink very efficiently. The flushing area can be enlarged, too.
In the case, the volumes of ink which should be jetted in the flushing operation may be larger for the nozzles jetting ink that has a greater rate of increasing viscosity. This flushing operation can recover the ability of the nozzles to jet ink very efficiently according to both the rate of increasing viscosity of the ink and the number of times the ink has been jetted. The flushing area can be enlarged, too.
In addition, the setting unit may set up the volumes of ink which should be jetted from the nozzles during the flushing operation according to the smallest one of the numbers of times counted by the jetting number counting unit. For example, the volumes of ink that should be jetted may be common.
A computer system can control the setting unit for setting up the volumes of ink which should be jetted from the nozzles in the flushing operation in such a manner that a volume of ink which should be jetted from a nozzle of a chosen class is set up separately from a volume of ink which should be jetted from a nozzle of another chosen class. The flushing operation controller can also be controlled by the computer to cause the driver to carry out the flushing operation of the nozzles so that volumes of ink actually jetted from the nozzles during the flushing operation are respectively coincident with the volumes of ink set up by the setting unit.
This invention includes a storage unit capable of being read by a computer, and storing a program for controlling the setting unit and the flushing operation controller in a computer system.
This invention also includes the program itself for controlling the setting unit and the flushing operation controller in the computer system.
Another ink-jet recording apparatus may include: a recording head having a plurality of nozzles, classified into at least two classes, a second driver for sucking ink from the nozzles to carry out a cleaning operation, and a jetting number counting unit for counting respective numbers of inkdrops that have been jetted from the nozzles belonging to the respective classes during a printing operation. A cleaning setting unit is also included for setting up volumes of ink which should be sucked from the nozzles during the cleaning operation in such a manner that a volume of ink which should be sucked from the nozzle belonging to the chosen class is set up separately from a volume of ink which should be sucked from a nozzle belonging to another chosen class according to the numbers of inkdrops counted by the jetting number counting unit. A cleaning operation controller causes the second driver to carry out the cleaning operation of the nozzles so that volumes of ink actually sucked from the nozzles during the cleaning operation are respectively coincident with the volumes of ink set up by the setting unit.
In the case, when the ink has a relatively greater viscosity, a large volume of the ink can be sucked from the nozzles in the cleaning operation to recover the ability of the nozzles to jet ink. Therefore, there is no problem caused by the difference in the respective rates of increasing viscosity depending on the frequencies with which the nozzles are used. This cleaning operation can achieve less wasted ink, and make the printing operation stable.
A computer system can control the jetting number counting unit, the cleaning setting unit, and the cleaning operation controller.
This invention includes a storage unit capable of being read by a computer, storing a program for controlling the jetting number counting unit, the cleaning setting unit and the cleaning operation controller in a computer system.
This invention also includes the program itself for controlling the jetting number counting unit, the cleaning setting unit and the flushing operation controller in the computer system.